Flotation process



Patented Nov. 12, 1940 6 UNITED STATES PATENT OFFICE nom'rron mooass No Drawing Application October 14, 1937,

Serial No. 169,072

8 Claims.

This invention relates to an improved process for the concentration of ores, more particularly it relates to a method for improving the efliciency oi froth flotation processes employing cationactive flotation agents. Still more particularly it relates to the use of assisting agents in froth flotation processes employing cation-active flotation agents; and still more particularly it relates to the use of assisting agents in froth flotation 10 processes for the concentration of negativelycharged minerals employing cation-active flotation agents.

This invention has as an object the development of an improved method for separating or u concentrating negatively charged minerals such as quartz and silicate minerals. A further object is to increase the selectivity of cation-active flotation agents in such processes. Another object is to provide an assisting agent which in combination with a cation-active collector produces a synergistic effect thereby'imparting to the combination a collecting power which is greater than that o! the sum of the elements of said combination. A still further object is the production of an improved process of concentrating metal carbonate and oxide minerals, using cation-active flotation agents and assisting agents. Other objects will appear hereinafter.

The above and other objects appearing hereinaiter are accomplished by the following invention which comprises adding to a pulp containing minerals and negatively charged gangue material a cation-active flotation agent and an 5 assisting agent and subjecting the same to a flotation operation. The valuable fraction of the ore may be found in the froth layer or it may remain in the cell. In this way a sharper separation of valuable mineral from gangue is effected, resulting in a purer product and greater recovery.

We have utilized the ability of surface-active cationic reagents to float siliceous minerals by means of a froth in preference to the indifferent metallic oxides and carbonates, and have improved the periormance of the cation-active flo tation agents, particularly in the separation of siliceous material from calcium carbonate, or

limestone, by the use of added assistants. These assistants, a great number of which act as dispersing reagents in other unrelated applications, promote separation of more of the siliceous material for a given amount of flotation agent resulting in the separation of a higher grade of 5 limestone with the same or higher recovery remaining behind as tailings. Another way of expressing the same effect is to state that in the majority of cases for the production of a desired 'grade of mineral concentrate a substantial re- 10 duction in the required amount of collector is made possible by the addition of an assistant. In certain instances an improvement in the collecting power of cation-active flotation agents is eflected by a preliminary acid leach which serves to remove mineral stains from quartz 15 particles and gives clean, readily floated quartz. Thus, in the case of the removal of silica from iron oxide minerals an improved performance in the collecting properties of cation-active agents results from leaching the ore with a. small amount of a mineral acid such as hydrochloric acid prior to the flotation step. This invention will be further understood but is not intended to be limited by the following examples:

Example I A sample of siliceouslimestone used in the production of Portland cement was employed in flotation experiments using assistants with cationic flotation reagents. The mineral composition of this limestone has been described in detail by B. L. Miller and C. H. Breerwood (Am. Inst. Mining Met. Engrs, Tech. Pub. No. 606, p. 15, February, 1935). Calcite, mica and quartz constitute the bulk of the rock. Pyrite, limonite, apatite, and amorphous carbon are present in small quantities.

The limestone was crushed in a small jaw crusher and then reduced to minus 40-mesh by 40 means of a Braun disc pulverizer. Slurries for use in flotation experiments were prepared by, grinding 1 kg. of the minus 40-mesh ore for 70 minutes in a one-gallon porcelain jar mill with one liter of water and 3 kg. of flint pebbles. The 45 ore particles were then about 84-86% minus ZOO-mesh.

The slurry prepared according to the above procedure was placed in a 1 kg. Denver Equipment Company flotation cell or the sub-aeration make - frothing agent consisted of the branched-chain,

oxygenated organic compounds prepared by the catalytic hydrogenation of carbon oxides under elevated temperatures and pressures as described in U. S. Patents 1,844,129, 1,844,857, and 1,939,708. The boiling range of the particular fraction of these oxygenated organic compounds used was 147-157 C.

With the addition of frother b a heavily loaded froth, dark gray in color, formed rapidly and was collected for 9 minutes, after which time there was no further collection of minerals or production of froth. The flotation concentrate and taillngs were filtered, dried, weighed, and analyzed for their calcium carbonate content. The results are summarized in the folio-wing table:

C110 0: GaOO: Weight CaC 0: Product weight percent (grams) pawn; (grams) recover Heads 1000. 7 1 75. 5 755. 6 Over-flows 245. 7 64. 70 159. 0 21. 1 Underflow 755. 0 79. 02 506. 6 78. 9

1 Calculated.

Reagents: Crude dodecyl amine hydrochloride, 0.025 g. or 0.05 lb.lton; Frother b, 0.07 g. or 0.14 lb./ton.

It will be noted from the table that 78.9% of the calcium carbonate remained in the cell in the underflow, commonly called the tailings in ore dressing terminology. Since the desired mineral concentrated in the underflow we have preferred not to use the term tailings as that term generally implies a waste product or gangue. Similarly we have used the term overflow to designate the product carried out of the cell by the froth. Generally, the product frothed out of the cell is called the concentrate but we prefer to avoid that term; since in its usual use it connotes a purification or segregation of valuable minerals and in our process the froth carries out the undesired minerals. The terms underflow and overflow" are therefore used to designate our flotation products rather than the commonly used terms, tailings and concentrate. In the above experiment the grade of limestone was increased from 75.5% to 79.02% of calcium carbonate with a recovery of 78.9%.

By crude dodecyl amine hydrochloride as used herein is meant the mixture of hydrochlorides of the higher primary aliphatic amines in which the alkyl groups correspond in carbon content and composition to the fatty acids occurring naturally in coconut oil.

in addition to the same quantities of crude dodecyl amine hydrochloride and frother b, 0.5

. ,gram of sodium phosphate. The flotation fractions were filtered, dried, weighed and analyzed,

as before.

Example III The process of Example I was repeated using, in addition to the same quantities of crude d0- decyl amine lwdrochloride and frother b, 0.50

solids. I

g. of sodium silicate corresponding to 1.0 lb./ton of heads.

In place of the assisting agents listed in the above examples, other water-soluble inorganic salts of inorganic acids can be used in the practice of this invention. Among the agents tested and found to have assisting properties are water soluble salts of silicic and phosphoric acids, e. g. sodium silicate and sodium phosphate.

In addition to the. cation-active agents disclosed in the examples, we have found that a very large number of other agents will give good results. Either single compounds or mixtures are useful. Among the agents which can be used to advantage in the separation of metal carbonates and oxides from siliceous gangues, the following may be mentioned:

The agents of our invention may be designated by the following general formula:

in which R is a non-aromatic (i. e. non-benzenoid) hydrocarbon radical of 8 to 22 carbon atoms; M represents pentavalent nitrogen or tetravalent sulfur; R represents hydrogen atoms or hydrocarbon radicals having not more than 5. carbon atoms which may be constituents of an alicyclic or of a heterocyclic ring; a: is an integer less by two than the valence of element M, and Y is a negatively charged salt fdrming atom or group, for example, chlorine, bromine, nitrate. acetate, chloroacetate, etc. The long chain aliphatic radical R need not be entirely composed of carbon atoms in the chain but may contain ether linkages, ester groups, sulfur atoms, carbonyl groups, etc. provided these groups do not introduce new centers of polarity. For example, reagents such as the hydrochloride of the dodecyl ester of alpha-amino-isobutyric acid, the hydrochloride of beta-aminoethyl dodecyl ether, and the hydrochloride of the dodecyl ester of alphaamino-isobutyric acid are good flotation agents for use in the process of this invention; such substances, however, as the hydrochloride of a long chain amine having a carboxyl group on the end removed from the amino group would not produce the desired effect, since another polar, soiubilizinggroup has been introduced.

Two types of reagents which at first glance appear to differ from the type formula set forth above have been found useful in the practice of this invention. One of these types comprises salts of amino naphthenes derived from naphthenic acids and rosin acids. In this case R contains about 11 to 19 carbon atoms, but inexamples of related compounds useful in.this in vention are given in Downing and 'Johnson Patent No. 2,129,264. Examples of such betaines are N-dodecyl betaine, N-cetyl betaine, N-deeyl betaine, C-dodecyl betaine, C-octadecyl betaine, etc.

The betaines are particularly effective if used in the presence of small amounts of mineral or organic acids and this observation may furnish a clue to their manner of action. It is possible that the betaine ring tends to open by addition of acid and the resulting product tends to ionize yielding a surface active cation.

A class of substances which we have found to be particularly eifective is composed of mixtures of salts of amines derived from the fatty acids obtained by hydrolytic splitting of natural fatty glycerides. For example, the mixture of amines derived from coconut oilfatty acids by the following series of reactions gives excellent flotation results after conversion to a water-soluble salt such as the hydrochloride or acetate.

We have found that a number of closely related substances which deviate in some way from the general formula set forth above entirely ineffective in the purification of iron ore by our flotation process. The following substances are examples of ineffective reagents:

Para-toluidine hydrochloride n-Amylamine-hydrochloride Dicyclohexylamine hydrochloride Quinoldine hydrochloride Ethylpyridinium iodide Diethyl cyclohexyl benzyl ammonium chloride The amount of cation-active flotation reagent required to produce the above effects varies somewhat with the reagent chosen and the particular ore being treated. In general, the amount needed will be between 0.05 and 2.0 pounds per ton of ore, but in some cases somewhat smaller or larger quantities may be required. Some of the reagents produce suflicient frothing so that an additional frothing agent is not required, while others have little or no frothing power. When greater frothing power is needed, we prefer to use a material such as pine oil, cresylic acid or frother b, since these frothers have no adverse effect on the selectivity of the collecting agents. Occasionally we flnd it advantageous to use mixtures of two or more of the cation-active reagents to produce flotation products of high quality. In carrying out a flotation process according to the teachings of this invention, any of the well known types of flotation cells may be employed. The ratio of pulp solids to water may vary from about 1:1 to 1:6. Ordinarily a neutral pulp is used, but in some cases it may be desirable to use an alkaline or acid pulp.

It will be clear from the above that one of the uses of this invention is the preparation of calcium carbonate of good quality from natural rocks whose calcium carbonate content is too low to be of technical value. By means of this process' limestone rocks containing 40-70% ,calcium carbonate can be purified to such an extent that the product :can be used in the manufacture of jPortland cement. It is also possible to prepare calcium carbonate concentrates approaching theoretical purity from low-grade limestone by this process." Theprocess of this invention also I permits the recovery of iron carbonate. manganese carbonate; magnesium carbonate, and other metallic carbonates from ores containing these minerals with other siliceous materials as impurities. Conversely it may be used to prep'aretalc, mica, or quartz products of high purity andyalue when the principal impurities are alkaline earth or heavy metal carbonates or'oirides; While the herein disclosed examples apply to "theiuse' of assistants in the beneficiation of calcium carbonate, the same principles apply to the concentration of oxidized iron minerals in which the cationic collectors are benefited through the use of assistants.

The present process affords two outstanding advantages as compared with previously known methods for the removal of siliceous minerals by means of cationic collectors. First, it provides a process by which quartz and siliceous minerals can be separated from other minerals at a substantial reduction in the amount of collector through the use of assistants. Secondly, with a given amount of cation-active agent, the use of an assistant increases the selectivity as a result of which a higher grade of mineral concentrate is obtained.

We claim:

1. The process of concentrating ores taken from the group consisting of metal carbonate and oxide ores containing siliceous gangue which comprises adding to the pulp a small amount of a cation-active material having the general formula:

in which R is a non-aromatic hydrocarbon radical of 8 to 22 carbon atoms; M is an element selected from the class consisting of pentavalent nitrogen and tetravalent sulfur; R is selected from the class consisting of hydrogen and aliphatic hydrocarbon radicals having not more than 5 carbon atoms, which aliphatic hydrocarbon radicals may be constituents of a carbocyclic ring of the class consisting of alicyclic and heterocyclic rings; Y is a negatively charged salt forming group and :c is an integer less by two than the valence of M and a small amount of a water soluble inorganic salt of an inorganic polybasic acid, subjecting the mixture to a flotation operation and removing the mineral as an underflow.

2. A froth flotation process for concentrating ores taken from the group consisting of metal carbonate and oxide ores containing siliceous gangue which comprises adding to the pulp a catiton active flotation agent and a small amount of a water soluble inorganic salt of a polybasic inorganic acid and subjecting the mixture to a flotation operation.

3. In a froth flotation process of concentrating carbonate minerals containing siliceous gangue involving the use of water soluble cation active notation agents which form a positively charged surface active ion, said agents containing a hydrocarbon radical of from 8 to 22 carbon atoms; the steps which comprise incorporating in the pulp a small amount of a water soluble inorganic salt of a polybaslc inorganic acid.

4. A process as set forth in claim 2 wherein the salt is sodium silicate.

5. A process as set forth in claim 2 wherein the saltis sodium phosphate.

6. A process as set forth in claim 2 wherein the cation active agent is used in an amount between 0.05 to 2.0 pounds per ton of ore.

7. The process of claim 2 in which the carbonate mineral is calcium carbonate.

8. The process of claim 2 in which the mineral contains non-magnetic oxides 01' iron.

JAMES EMORY KIRBY. JOSEPH LELNCOIN GILL-SON.

7 CERTIFICATE UF CORRECTION. Patent No. '2,2'21,L;85. November "12, 191p.

" JAMES more KIRBY, ET AL.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correctionas follows: Page 2, first column, line 7 for "induct", read --induceline 28, in the heading to the table, last column thereof, for the word "recover". read --recovery-; and second column, line 62, for agentg read -'-reagents; page 5, sec-- 0nd column, line 711., claim 2, for "catiton" read -cation--; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 1mm day of January, A. D. 19!;1.

Henry Van Arsdale,

(Se-a1) Acting Commissioner of Patents. 

